Floor weight capacity – hold a 125kg bath?

We are changing our bathroom soon, and like the look of a limestone resin bath.

The bath weighs 125kg empty. The bathroom is on 1st floor, and I assume the floor is ‘normal’ construction with ply board laid on top of the joists/floorboards.

Bath 125kg
Water 200kg
Person 80 kg

Total 400kg to focused through a 0.90m x 0.50m contact patch.

Normal baths weigh approx 60kg. Am I thinking about this too much?

Thanks

Normal baths weigh approx 60kg

What about when it’s full? The new one weighs 325 kg full. The key thing is the difference between the total weight. If it’s supported properly so the weight is transferred to the joists, it shouldn’t be a problem. That’s like four people standing together having a big hug.

Probably.

Would you even have given it a second thought if you had a regular bath and weighed 145kg? That’s same gross load.

Also, if you are considering the weight with it full to the brim, putting a person in will displace pretty much the same weight of water as the person weighs. The maximum weight will just be the bath plus its capacity in litres converted to kilograms.

The maximum weight will just be the bath plus its capacity in litres converted to kilograms.

No 125kg is definitely the dry weight (its in essence a stone bath). Total water capacity to full is 280 ltrs. But yes had missed the fact that weight of a person displaces the weight of water.

Two people one bath, same weight. Would you worry? I have no idea what the actual answer is.

I’d consider the specific location relative to joists and any support walls. I’d want it against a supporting wall and over several joists rather then in the middle of a room over fewer joists.

its capacity in litres converted to kilograms

The conversion here is to cross out ‘L’ and write ‘kg’. It’s the same. In’t metric brilliant!

Two people one bath, same weight.

I think I’ve seen that video.

A farming acquaintance used to put the “luck money” he got from selling stock at market into an old milk churn next to his bed. One evening he emptied a few quid out of his pocket and the milk churn went through the floor and landed in the kitchen.
I reckon a bath won’t be a problem due to its footprint, but it would be a good idea to see how the load is transferring to the joists and how many are supporting it. Also the closer to the wall that the joists are attached to the better.
I suspect the milk churn wasn’t supported by any joists at all and just had to go through some floorboards and plaster.

Potentially 400kg spread over [probably] 3 joists – should be OK I would have thought (130kg/joist), especially if the bath is near the wall.
If you’re fancy and want the bath in the middle of the floor for some reason it may be more interesting and lead to some sag depending upon joist size.

But yes had missed the fact that weight of a person displaces the weight of water.

But who fills the bath to the brim and then gets in? Fill the bath with water to 2/3rds full (say 160L/kg) then add 80kg of person = about 240kg + the dry weight of the bath.

But who fills the bath to the brim and then gets in? Fill the bath with water to 2/3rds full (say 160L/kg) then add 80kg of person = about 240kg + the dry weight of the bath.

I don’t think anyone is suggesting this is the way people run a bath, more that the calculations were off and in effect had some double counting in them.

But who fills the bath to the brim and then gets in?

It’s easy to forget you started filling a bath and have it overflow. The floor needs to be strong enough to support it if it’s filled to the brim. It will weigh pretty much the same if a person were to be in it. Therefore the weight of the bath plus enough water to fill it to the brim is the maximum weight.

Therefore the weight of the bath plus enough water to fill it to the brim is the maximum weight.

Unless two people stand in the bath 😉

Unless two people stand in the bath 😉

Oh good point!!
I bet you could get 4 people standing in a bath!

Unless two people stand in the bath

The conversion here is to cross out ‘L’ and write ‘kg’. It’s the same. In’t metric brilliant!

Only if you like your bath at 4oC.

putting a person in will displace pretty much the same weight of water as the person weighs

What if they are a very very dense but tiny person, or the size of a small planet and full of nothing but farts?
Or if the bath is on a conveyor belt?

Unless two people stand in the bath

And how does the load vary if they start bouncing?

I await the thread regarding getting the bath up the stairs and through the door

Or if the bath is on a conveyor belt?

If the bath is on a house boat, on an aquaduct, on a canal that is a closed body of water, will the aquaduct bridge need to be stronger if the bath is full Vs if the bath is empty?

What if there is two people and this so called “bouncing” matches the resonant frequency of the joists?

But who fills the bath to the brim and then gets in?

Girls do when they are eating a Flake.

My missus wanted a stone bath but the builders talked her out of it saying the floor wouldn’t take it. In hindsight I reckon it was just that they didn’t want to have to carry the thing upstairs.

I await the thread regarding getting the bath up the stairs and through the door

Did that with a cast iron bath up an older (steeper than normal) staircase, was not fun.

Don’t bathrooms generally have doubled up joists to take the loads?

How olds the house? What state is the subfloor in, what’s the existing flooring? Is the bath freestanding or in an alcove? If freestanding, are you installing it on top of large format tile
The deflection of the flooring for tile is probably the bigger concern.

Don’t bathrooms generally have doubled up joists to take the loads?

I doubt it. Modern joists are massive though, about twice the size of the ones in our Victorian house.

MrsRNP had similar ideas but with a cast iron claw foot bath in our Victorian cottage refurb.

I worked on weight of full bath and two people standing in it.

Our floor boards were rotten from previous leaking bath. I ended up dropping the kitchen ceiling and installing two 200mm (iirc) C/channel sections bolted either side of the load bearing joists with a few centre line holes bored through with welded ring reinforcement round them for services to pass throigh (did it at work as a foreigner). Probably a bit overkill but didn’t want to end up in the kitchen when washing my neither regions….

I ended up dropping the kitchen ceiling and installing two 200mm (iirc) C/channel sections bolted either side of the load bearing joists with a few centre line holes bored through with welded ring reinforcement round them for services to pass throigh (did it at work as a foreigner). Probably a bit overkill but didn’t want to end up in the kitchen when washing my neither regions…

You need to coat them in Teflon in case the kids make a mess of things.